1. Field of the Invention
The present invention generally relates to the monitoring of signals (e.g., voice and tones) transmitted over a communications link, and optimizing tone processing parameters based on the type and timing of the monitored signals.
2. Background Information
Cable-based IP telephony is a simplified and consolidated communication service that can be provided at a lower cost than consumers currently pay to separate Internet, television and telephony service providers. The use of the Internet for real-time voice applications is rapidly increasing. The goal of Internet Protocol (IP) telephony employing cable modem technology is to combine telephony, video, and data signals over a cable distribution infrastructure.
The Voice over IP (VoIP) gateway bridges the public switched telephone network (PSTN) or integrated services digital network (ISDN) with the packet-switched data network (TCP/IP based Network). Such a VoIP gateway is configured to provide IP call control and IP data transport, which includes the compression and decompression of voice channels. VoIP is a relatively new service capable of being supported by Data Over Cable Systems Interface Specification (DOCSIS) cable networks. DOCSIS describes a standard for the cable modem interface between a cable TV operator and a computer.
DOCSIS has been accepted as the standard for devices that handle incoming and outgoing data signals across this interface. DOCSIS 1.0 was ratified by the International Telecommunication Union (ITU) in March 1998. Cable modems conforming to DOCSIS are available in many areas where cable operators operate. DOCSIS is an evolving standard which specifies modulation schemes and protocols for exchange of bidirectional signals over cable, allowing version 4 IP traffic to achieve transparent transfer between the Cable Modem Termination System-Network Side Interface (CMTS-NSI) and the Cable Modem to Customer Premise Equipment Interface (CMCI). Upgrades to existing cable modems and DSPs to maximize VoIP quality can be achieved by changing the programming in their EEPROM flash memory.
IP telephony links supporting modems and faxes often falsely detect modems and fax tones. Such a false detection can cause system parameters to be adjusted for fax/modem operation, rather than for voice. The detection of false tones can occur due to background noise detected during voice communications between users of a communications system. Such background noise may include modem tones outputted by a speaker in the same room as a user who is verbally conversing with another user over a communications link. Modem, fax or other tones can sometimes be heard during a television program or radio show. The false detection of one or more modem or fax tones (e.g., 2100 Hz signals), commonly found in music and other noise sources, can be disruptive to a normal voice conversation taking place over an IP telephony link, because the system monitoring the link automatically makes adjustments to support fax and modem communications.